Nephrotic syndrome

Nephrotic syndrome is a kidney disorder characterised by high levels of protein in the urine and swelling of body tissue.

People of any age can be affected by nephrotic syndrome, although children aged between 18 months and four years are at increased risk. Treatment involves controlling symptoms and treating the underlying condition that is causing the nephrotic syndrome.

Long-term nephrotic syndrome can result in permanent kidney damage leading to kidney failure, necessitating treatment with dialysis or, eventually, kidney transplant.

General information 

Nephrotic syndrome produces a collection of symptoms and signs that occur because tiny blood vessels (the glomeruli) in the kidneys sustain damage and do not function correctly.

The syndrome is characterised by abnormally high levels of protein in the urine (particularly one called albumin) and abnormally low protein levels in the blood. This often leads to fluid retention in the body tissues causing swelling (oedema) and can be associated with high blood cholesterol levels and high blood pressure.

The glomeruli act as filters to remove waste products from the blood, which are then excreted from the body in the urine. In nephrotic syndrome these filters become defective and leak, allowing large quantities of protein to be lost in the urine. Protein in the blood acts to prevent water entering the body’s cells. Reduced blood protein levels cause water to leak into body tissue, causing swelling.

Causes

In New Zealand, the most common cause of the nephrotic syndrome is glomerulonephritis — a group of kidney diseases where the glomeruli become inflamed. Malfunction of the immune system is thought to be the underlying cause of glomerulonephritis. For some reason, the immune system attacks and damages the glomeruli.

The three most common forms of glomerulonephritis causing nephrotic syndrome are:

• Minimal change nephropathy (also called minimal change disease).

• Membranous glomerulonephritis.

• Focal segmental glomerulonephritis.

Some forms of heart failure can cause nephrotic syndrome, as can a blood clot that forms in a kidney vein (renal vein thrombosis). There is also a rare form of the condition called congenital nephritic syndrome, which is genetic in origin and is present at birth.

A wide range of other disorders (including amyloidosis, diabetes, and systemic lupus erythematosus) and factors such as exposure to toxins are less common causes of the nephrotic syndrome.

In children, nephrotic syndrome is normally detected between the age of 3 and 4 years old. Most children have the form of glomerulonephritis called minimal change nephropathy. This is where minimal or no glomerular abnormalities are noted by a microscope. This form of nephrotic syndrome affects approximately 1 in 50,000 children. It can usually be successfully treated.

In adults, membranous glomerulonephritis and focal segmental glomerulonephritis are the most common causes of the nephrotic syndrome.

Signs and symptoms

Signs and symptoms include:

• Foamy urine

• Fatigue and weakness

• Swelling, especially around the eyes, hands, feet, and abdomen

• Loss of appetite

• Increased weight from fluid retention

• High protein levels in the urine and low protein levels in the blood.

As the condition progresses there may be:

• Susceptibility to infectious diseases due to an impaired immune system

• An increased risk of blood clots (thrombosis)

• Muscle wasting (due to the loss of protein)

• Malnourishment

• Weakening of the bones

• Abnormally low or abnormally high blood pressure

• High blood cholesterol levels

• Kidney failure.

Diagnosis

A referral to a nephrologist (kidney specialist) may be required for a diagnosis to be made. The doctor will take samples of the blood and urine. If results show large amounts of protein in the urine and decreased amounts of protein in the blood, the doctor may recommend a kidney biopsy.

A kidney biopsy is where a tiny piece of kidney is removed by a needle and studied under a microscope. This procedure usually involves a one-day stay in hospital and is performed under a light general anaesthetic or a local anaesthetic. Ultrasound scanning of the kidneys may also be performed.

Treatment

Treatment will depend on the underlying cause of the condition and is aimed at alleviating symptoms and preventing complications.

Medications that reduce the inflammatory effects of the immune system on the glomeruli are the mainstay of treatment. Medications to achieve this include corticosteroids (eg: prednisone) and potent immune-suppressing medications.

Medications to reduce high blood pressure and high blood cholesterol levels may also be prescribed. Blood-thinning medications (anticoagulants) may be prescribed to reduce the risk of developing blood clots.

The doctor may also recommend restricting fluid intake or may prescribe medications that increase the amount of urine produced (diuretics). These, along with bed rest, will help to reduce swelling.

The doctor or a dietitian may recommend a special diet aimed at controlling levels of protein, salt, and cholesterol in the body. Overall, it is important to maintain good health and nutrition and to ensure other medical conditions are treated promptly.

Further information and support

Kidney Health New Zealand (formerly the Kidney Foundation) offers support, information, and education about kidney disease. Details about local support groups are available on the website. Contact details are:

Kidney Health New Zealand

Freephone: 0800 543 639 (0800 Kidney)

E-mail: [email protected]

Website: www.kidneys.co.nz

References

Cohen, E.P. (2020). Nephrotic syndrome (Web page). Medscape Drugs and Diseases. New York, NY: WebMD LLC. https://emedicine.medscape.com/article/244631-overview [Accessed: 25/11/20]
Kidney Health New Zealand (2008). Nephrotic syndrome in children: What is nephrotic syndrome? (Information Sheet). Christchurch: Kidney Health New Zealand. https://www.kidneys.co.nz/resources/file/nephrotic_syndrome_in_children_03.pdf
Mayo Clinic (2020). Nephrotic syndrome (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/nephrotic-syndrome/symptoms-causes/syc-20375608 [Accessed: 25/11/20]
O’Toole, M.T. (Ed.) (2017). Nephrotic syndrome. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MO: Elsevier.

Last Reviewed: December 2020

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